A Muslim student who had been planning to join Islamic extremists in Syria has been jailed in Britain for 3 Â½ years. David Souaan was sentenced Tuesday after having been found guilty in December of preparing for terrorist acts. The 20-year-old Souaan had visited Syria in 2013 and was trying to returning there when he was arrested at Heathrow Airport in May. Judge Peter Rook said Souaan had been “vulnerable to extremist views” because of his youth and immaturity. Souaan came to Britain in 2013 on a student visa to study international relations at Birkbeck College in London. British officials say hundreds of Britons have joined extremists in Syria. Security officials warn that many may try to launch terror attacks inside Britain when they return.